Thermostatic bimetals

ABSTRACT

A thermostatic biemetal having a relatively high deflection is disclosed. The bimetal comprises as a high expanding side a manganese-nickel-copper alloy having specific ranges for nickel and the combined total of copper and one-half the nickel content is also within specific limits. The low expanding side is a nickel-iron-cobalt alloy with controlled amounts of manganese carbon and silicon.

United States Patent Gottlieb et al.

[ Oct. 16,1973

2,349,577 5/1944 Dean 29/1955 3,581,366 6/1971 Gottlieb ..29/195.5

Primary Examinerl-lyland Bizot Attorney-Norman J. OMalley et a1.

[57] ABSTRACT A thermostatic biemetal having a relatively highdeflection is disclosed. The bimetal comprises as a high expanding sidea manganese-nickel-copper alloy having specific ranges for nickel andthe combined total of copper and one-half the nickel content is alsowithin specific limits. The low expanding side is-a nickel-iron-cobaltalloy with controlled amounts of manganese carbon and silicon.

2 Claims, 1 Drawing Figure I6 /\BIMETAL OF THIS INVENTION PRIOR ARTBIMETAL TEMPERATURE "F 1 THERMOSTATIC BIMETALS CROSS-REFERENCE TORELATED APPLICATIONS Co-pending patent application Ser. No. 244,530, 5filed Apr. 17, 1972, discloses'the high expanding alloys used in thisinvention and filed concurrently herewith. Those alloys, however, can beused in other uses.

BACKGROUND OF THE INVENTION This invention relates to thermostaticbimetals. More particularly it relates to a thermostatic bimetal havingan extremely higher deflection.

Thermostatic bimetals have long used a 36 Ni balance iron alloy as a lowexpanding alloy and the most common high expanding alloys were theMn-Ni-Cu alloy containing from about 16 to 18 percent copper and aboutpercent nickel because it was believed these alloys had the maximumdegree of thermal expansion of any of the alloys of the Mn-Ni-Cu system.These bimetals have a specific deflection of about 0.20 X 10 /C to 0.21X lO/C when tested in the temperature range of from about 20C to about130C.

The Mn-Ni-Cu alloys disclosed and claimed in the before-mentionedco-pending application result in a larger deflection when used with thetraditional 36 percent nickel balance iron alloys known as INVAR thanthe prior art combination of INVAR and Mn 10 Ni l618 Cu. It is believed,however, that a bimetal that has an even higher deflection would be anadvancement in the art.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of this inventionto provide a bimetal having a high deflection.

It is another object of this invention to provide a bimetal which willyield the same amount of deflection with appreciably less length.

It is still another object of this invention to provide a bimetal whichhas a specific deflection of greater than 0.23 X 10/C when measured inthe temperature range of from 20 to 130C.

These and other objects are achieved in one aspect of this inventionwhich comprises a bimetal having as its high expanding side an alloyconsisting essentially of from about 15.5 percent to about 22.5 percentby weight of nickel, the sum of the percent of weight of copper andone-half of the percent by weight of nickel being from about 13.75percent to about 16.75 percent and the balance manganese. The foregoinghigh expanding alloy is used in conjunction with a low expanding alloyhaving the following constituents in percent 55 by weight:

BRIEF DESCRIPTION OF THE DRAWING The drawing is a graph which shows thedifferences in coefficient of expansion between the high and lowexpanding elements of a prior art bimetal and the bimetal of thisinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For a betterunderstanding of the present invention, together with other and furtherobjects, advantages and capabilities thereof, reference is made to thefollowing disclosure and appended claims in connection with the abovedescription of some of the aspects of the invention.

A typical thermostatic bimetal is sold by W. M. Chace and designated asChace 6650. This bimetal consists of a high expanding alloy of 72% Mn,10% Ni and 18% Cu and a low expanding alloy of 36% nickel, balance iron.The specific deflection is about 0.202 X l0/C. The specific deflectionis obtained on a standard dimension of a bimetal such as 1 mm thick X mmlong and heated over the temperature range of from 20C to C. Thedeflection is determined by clamping one end and measuring thedeflection of the other end. The deflection is dependent primarily uponthe difference in the coefficients of expansion of the materials.

It has been found that the bimetals of this invention yield a highspecific deflection of at least 0.23 X 10/C over the foregoingtemperature range. This enables less length of metal to be used to getthe same deflection. The high expanding alloy consists essentially offrom about 15.5 to about 22.5 percent by weight of nickel, the sum ofthe copper content in percent by weight and one-half the nickel contentin percent by weight within the range of 13.75 to 16.75 and the balancemanganese. Preferred alloys within the foregoing ranges are those thatcontain from about 15.5 percent to about 18.5 percent by weight ofnickel. The coefficient of expansion of these alloys is greater thanabout 30.0 ppm/*C.

The low expanding alloys are iron, nickel and cobalt alloys containingspecific amounts of manganese, carbon and silicon. These alloys arefurther characterized by having narrow ranges of each component that isfrom 30.75 to 31.75 percent by weight nickel, 6.5 to 8.5 percent cobaltand balance iron. Manganese varies between 0.05 to 0.5 percent, carbonfrom 0.015 to 0.12 percent and silicon from 0.015 to 0.15 percent.

The difference in the coefficients of expansion in the alloys used inthe bimetals of this invention as compared with the prior art bimetal isshown in the drawing over the range of 100 to 290F. As can be seen, forall temperature values shown the differences which relate directly todeflection are appreciably greater for the bimetal of this invention.For example, the differences of the expansion metal used in the bimetalsof this invention are about 3.5 to 3.8 ppm/C greater than those of themetals used in prior art bimetals in the 200 to 400F range.

While there has been shown and described what are at present consideredthe preferred embodiments of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the scope of the invention as defined bythe appended claims.

What is claimed is:

1. A bimetal comprising a high expanding side of an alloy consistingessentially of from about 15.5 to about 22.5 percent by weight ofnickel, the sum of the copper content in percent by weight and one-halfthe nickel content in percent by weight being from about 13.75 to about16.75 percent and the balance manganese, and f metallurgically bonded toa common interface of said 23 13::

high expanding side, a low expanding side of an alloy consistingessentially of in percent by weight: 2. A bimetal according to Claim 1having a specific 5 deflection of at least about 023 X lO/C within thenickel 30-75 to 31-75 temperature range of from about to about 130C.cobalt 6.5 to 8.5

manganese 0.05 to 0.5

2. A bimetal according to Claim 1 having a specific deflection of atleast about 0.23 X 10 4/*C within the temperature range of from about20* to about 130*C.